Grasshopper mice are extremely aggressive predators. They are largely nocturnal, good climbers, and active year round. They hunt their prey like most sophisticated predators. After stalking their potential kill, they seize the animal with a rush, killing with a bite to the head. While overpowering their prey, O torridus closes its eyes and lays its ears back.
They also apparently eat their mates (that's one way to solve a domestic dispute):
Grasshopper mice are solitary animals, guarding their large territory fiercely against all intruders. They may, however, live in male-female pairs year round, although this seems to shorten the life span, as one of the two partners inevitably kills the other. Grasshopper mice often commit acts of cannibalism, killing and eating other members of their species if they are threatened or in need of food.
Holy shit, they howl too??
Perhaps the most unusual thing about the grasshopper mouse is its trademark "howl". Onychomys can produce a loud, piercing, pure tone, which lasts between 0.7 and 1.2 seconds, and is audible to the human ear up to100 meters away. Standing on their hind legs with their noses pointed upwards, they give this call when faced with an adversary, including other grasshopper mice, or prior to making a kill. This shrill warning, often repeated, is compared to a miniature wolf call, due to its smoothness and prolongation, and to the animal's wolf-like posture.
Damn, these are badass little smammals.
This is why I got into Biology and wanted to study in particular small mammals (smammals) because of all the crazy, cool shit they do.
Read more here.